Electronic Structure of Magnetic Endohedral Fullerenes and Application of Self-Interaction Correction to Atoms

Abstract

Endohedral fullerenes, which represent a novel family of carbon nanostructures, are fullerene cages with atoms, ions or clusters trapped in their cavities. The encapsulated molecule or cluster can determine the properties of the fullerenes as charge transfer often occurs from endohedral unit to the outer cage leading to high stability. Endohedral fullerenes hold a lot of fascinating properties with potential applications in biomedicine, molecular electronics and photonics etc. In this work, novel endohedral fullerenes containing transition metal oxide cubane cluster are studied for possible magnetic properties. The motivation is to examine whether the encapsulation can lead to stabilized transition metal clusters with high magnetic anisotropy energy. The electronic and magnetic properties of Co4O4@C70, Co4O 4@C76, Co4O4@C78, Co 4O4@C80, Mn4O4@C70 , Mn4O4@C76, Mn4O4 @C78 and Mn4O4@C80 are calculated using density functional theory. The magnetic anisotropy energy of these endohedral fullerenes is calculated using a perturbative approach for including the spin-orbit interaction. The density functional theory calculations employ approximations to the exchange-correlation functional, which are not free from self-interaction. The self-interaction leads to delocalized d-orbitals and can lead to incorrect spin states in some systems. We test the recently developed self-interaction correction scheme based on Fermi-Lowdin orbitals. The final motivation is to apply the scheme to transition metal based systems. In this proposal we present the preliminary work done using the Fermi-orbital based scheme to closed-shell atoms. In future, this work will be extended to transition metal oxide clusters.